Per feed-average color

Hi there,

As shortly discussed here: http://tt-rss.org/forum/viewtopic.php?f=10&t=1576&p=9150#p9150

This is the first working draft - the only thing missing is some error logging and switching the feeds' title to white if the favicon colors are too dark. It's already fully working:
http://i.imgur.com/HFkvv7S.png

You know your solution better and you know better how to integrate things. I added a new column to the feeds table holding the average color information - maybe you want to do it differently.

Cheers,
Dennis